How can I tell if ethanol, or E85, is "actually" cheaper to use than gas?

Question

I know that ethanol is less efficient than gas, therefore you have to fill up more often and get less mpg. So my question is, is there some type of formula to tell if it is indeed cheaper to use E85 as opposed to gas by their current price gap?

Answer 1

The typical decrease in mileage when using E-85 is 27%.  To calculate your mileage on E-85 take your current mileage and multiply by .27.  The number you get from that you will then subtract from your current mpg.  

Example: 15mpg (gas)X0.27= 4.05

                  15-4.05= 11.95mpg (E-85)

Now get the prices for both gas and E-85.  Choose a distance for instance how many miles you drive a week.  Divide that by your mpg, you'll need to do it twice once with gas mpg and once with E-85 mpg.  This will tell you how many gallons you will use for that distance

Example:  Distance: 300 miles

                  Gas mpg: 15mpg

                  300 miles/15mpg= 20 gallons of gas

                  Distance: 300 miiles

                  E-85 mpg: 11.95mpg

                  300 miles/11.95mpg= 25 gal (rounded) of E-85

After you figure out how many gallons you will use on gas and on E-85, get the prices for both gas and E-85.  Now multiply the cost of gas by the gallons of gas, then do the same with the cost of E-85 and the gallons of E-85.  This will tell you how much you will spend on each to go a given distance.

Example:  Gas: $3.98

                  Gallons: 20

                  $3.98 X 20gal= $79.60

                   E-85: $3.29

                   Gallons: 25

                   $3.29 X 25gal= $82.25

Based on the prices I used, which I went to http://www.e85prices.com, and got an average price of both gas and E-85.  It is cheaper to use gas.  They also have a calculator on their website that you can use to calculate what is cheaper.

Answer 2

See the web site below.

It will tell you the local E85 prices and the local gasoline prices. This will help you find the cheapest E85 in your area.  In general, the more E85 fueling stations in your local area, the competition will cause it to be more competitively priced.

The page will have a handy calculator.

You enter the average fuel mileage for your vehicle while running on gasoline. You also enter the average fuel mileage for your vehicle while running on E85.  You then enter the local price of E85 and gasoline.  This will calculate for you the cost per mile to drive on E85 compared to the cost per mile to use gasoline.

The cost of E85 varies widely.  Like gasoline, there is no regulation on what should be charged.   Some stations charge as much as 37% less for E85 than gasoline.  If you are lucky enough to have this station near you, you will definitely come out ahead using E85.  Some charge as little as 6% less than gasoline. If you use E85 priced at 6% lower than gasoline, it will be cheaper to use gasoline.

On average, you break even or come out ahead when you pay at least 20% less for E85 than gasoline.